Recently, power plant designs have required the addition of desulphurization systems to meet increasingly stringent regulations on the emission of sulfur dioxide (“SO2”). Power plants may include flash dry absorber (“FDA”) scrubbers downstream of a boiler to reduce the emission of SO2. FDA scrubbers are frequently used in power plants employing circulating fluidized bed (“CFB”) boilers.
A typical FDA scrubber functions as part of a power plant's particulate collection system; particulate herein being synonymous with flyash, ash or dust, a byproduct of combustion in the boiler. The FDA scrubber may include various particulate collection mechanisms such as a fabric filter, an electrostatic precipitator, etc. The fabric filter may also be referred to as a baghouse.
In operation, flue gases with entrained particulates enter the FDA scrubber via a reactor column. The flue gases pass through the reactor column and into an inlet duct of the FDA scrubber particulate collection mechanism. The flue gases then interact with the particulate collection mechanism wherein the particulates suspended in the flue gases are removed. The removed particulates are then passed through a mixer-hydrator and injected into the reactor column. The recycled and humidified particulates then react with un-filtered flue gases before being re-introduced into the particulate collection mechanism.
Residual calcium oxide (“CaO”) in the particulate produced by the boiler functions as a sorbent for SO2 capture. The hydrated particulate including the residual CaO reacts with the flue gases in the reactor column and in the particulate collection mechanism to remove SO2 therefrom.
The use of an FDA scrubber alone may not be adequate to remove enough SO2 to meet today's stringent emission requirements. Typically, an FDA scrubber may be supplemented by other SO2 reduction systems, such as a limestone feed system which introduces limestone into a power plant's boiler. Similar to residual CaO of the particulate mentioned above, the limestone functions as a sorbent for SO2 capture.
While the abovementioned such sulfur dioxide reduction systems have proven effective, they may also be expensive to implement and operate. Costs of such systems include an increase in the amount of fuel used to compensate for a reduced catalytic efficiency due to the introduction of the limestone into the boiler and the cost of the limestone itself. The introduction of limestone to the boiler also results in the catalytic generation of nitrogen oxide (“NOx”). The emission of NOx is also regulated, and may require its own costly removal systems.
Accordingly, a system and method for reducing costs, increasing efficiency, and reducing SOx and NOx associated with the use of present sulfur dioxide reduction systems is desired.